Protective masks which are worn for protection against chemical and biological gas or vapors have gained significant acceptance in recent years. These devices have been provided with filters which remove most of the objectionable or hazardous materials, enabling the user to function in otherwise difficult environments.
One major advance in protective masks of this type has been the use of canister filters which contain an effective amount of filtering material. These canisters are replaceable so that the mask itself remains with the individual who regularly uses it and allows that person to replace the filter when it has been overused or exhausted. One form of canister type protective mask device which has been in use is known as a high profile canister filter.
These filters are, as originally designed, difficult to use for several reasons. One drawback with these devices is the difficulty in changing the filter during extended use without exposing the user to unfiltered atmosphere. Some prior art designs are such that the mask must be removed in order to change the filter, making that operation possible without risk to the user only after completion of the activity during which exposure is possible. The time that the device can be used is therefore limited to the length of time that the filter can be safely used before it is saturated or clogged or otherwise in need of replacement.
Another major problem is that mounting the canister on the face of the mask produces an orientation which is prominent and even at time awkward. Sometimes during maneuvers, hard contact with the canister occurs which results in the face seal of the respiratory protective device being broken. That, of course, defeats the entire purpose of the mask and exposes the user to a high risk.
In prior art designs in which the canister is mounted on the face of the protective mask, users have often experienced tiring of the neck muscles because of the weight and awkward orientation of the canister on the mask. No current negative pressure respiratory protective devices display methods to alleviate this problem.
Accordingly, an object of this invention is to provide a filter which can easily be replaced without adversely exposing the user to a great risk of contact with the environment from which the user is being protected.
Another object of this invention is to provide a design for a filter for a protective mask which does not place an undue strain on the muscles of the user because of awkward orientation and weight of the canister on the mask.
Yet another object of this invention is to provide a filter device which is not at risk of being unnecessarily contacted during use.
Other objects will appear hereinafter.